Manufacture of styphnic acid salts



Patented Mar. 3, 1942 9 Willi Briin, Bridgeport, Conm, assignor toRemington Arms Gompany, Inc., a corporation of Delaware N Drawing.Application November 28, 1940, Serial No. 367,607

2 Claims.

This invention relates to the manufacture of styphnic acid and certainof its salts, and contemplates improvements and refinements in theproduction of styphnic acid, the practice ofwhich results in a productadapted tobe made into salts having certain desirable propertiesandcharacteristics.

The present application is a continuation in part of my prior co-pendingapplication, Serial No. 207,782, filed May 13, 1938, which is a divisionof application Serial No. 674,049, filed June 2, 1933, now Patent No.2,137,234, November 22, 1938.

More specifically, the invention contemplates the control of the shapeand form ofthe crystals of certain salts of styphnic acid, particularlybasic. lead styphnate, and certain methods in the manufacture ofstyphnic acid which enable the acid to form salts having novel anddesirable crystal shapes.

The manufacture of basic lead styphnate, and particularly a redcrystalline form thereof is described in. this applicants Patent No.1,942,274, January 2, 1934. It may bebriefly summarized as follows:

A solution of styphnic acid and sodium hydroxide, in the proportions of12.2 grams of styphnic acid and 8 grams of sodium hydroxide in 400 c. c.of water, is dropped into a lead nitrate solution of the concentrationof about grams of lead nitrate in 350 c. c. of water. The temperature ismaintained between and C., and the styphnic acid-sodium hydroxidesolution is at first dropped into the lead nitrate solution very slowly.The first precipitate is a previously known yellow amorphous or partlyamorphous basic lead styphnate which, if the sodium hydroxide-styphnicacid solution is at first introduced quite slowly, changes over to aheavier red crystalline basic lead styphnate which quickly settles out.

When in the practice of the process above outlined ordinary styphniclead is used, the crystals of basic lead styphnate are rather thickhexagonal plates. They are less fragile and sensitive to friction andshock than the previously known yellow needle crystals. The presentinvention comprises the discovery of other crystalline forms of basiclead styphnate, and methods for producing basic lead styphnate in theseforms. The novel crystal shapes result from the use of styphnic acidmade in accordance with certain procedures constituting a part of thepresent invention. Th manufacture of ordinary styphnic acid will first'bebriefly described:

The raw material is resorcine (CsH4(OH)2). By treatment withconcentrated sulphuric acid, resorcine is sulphonated toresorcine-di-sulphonic acid, C6H2(OH)2(SO3H)2. Theresorcined-i-sulphonic acid is then nitrated with concentrated nitricacid. The precipitated styphnic acid is separated from the residue bycentrifugal action or by filtration, and subsequently washed, first witha dilute mineral acid and then with Water. If the sulphonation of theresorcine is complete, the resulting product is pure styphnic acid of abright yellow color and low gravimetric density, from which crystallinesalts are formed only with great difiiculty.

The present invention comprises the discovery that the character of thestyphnic acid may be altered in such a way as to control the crystalshape of the salts which it forms by the addition, during. the operationof sulphonating. of small amounts. of certain foreign substances. Suchvariations in the styphnic acid and in the crystal shapeof its salts,particularly the basic lead salt, are produced by the use of any one ofa number of different substances- Moreover; each substance has theproperty of producing its. own characteristic effects and crystal shape,each of these shapes. differing from the others. For example, if to abatch comprising grams. of resorcine and 460 c. c. of 98% sulphuric acidthere be added 10 c. c. of concentrated nitric acid, the resultingstyphnic acid is darker in color and less voluminous and its salts havedifferent physical properties. The further addition of .1 gram oftri-oxy-methylene results in a styphnic acid which yields its basic leadsalt in crystals of a shape differing very substantially from the usualcrystals of this salt. Said crystals are somewhat elongated square orrectangular prisms, as distinguished from the usual hexagonal plates,and appear to be more sensitive to shock and friction than the hexagonalplates. Two opposite faces of the rectangular prismatic crystals appearto be substantially square, while the other faces are rectangles havinga length of the general order of three or four times their width.

The use of catechol in place of tri-oxymethylene produces a styphnicacid whose basic lead salt likewise forms in square prismatic crystals,but these crystals are much shorter (more nearly cubical) than thoseresulting from trioxy-methylene. The procedure is as follows: Thecrystal controlling agent is preferably introduced into the sulphonatingsulphuric acid. Just as with tri-oxy-methylene, improved results aresecured if a small amount of nitric acid is also used. In 460 c. c. of98% sulphuric acid there is mixed 10 c. c. of concentrated nitric acidand .5 gram of crystalline catechol. The acid thus prepared is pouredover 110 grams of resorcine, this being the usual procedure in thesulphonation of resorcine. The manufacture of styphnic acid and thesalts thereof, such as the basic lead styphnate, is then completed inthe manner heretofore described.

The use of glucose in place of tri-oxy-methylene or catechol as abovedescribed produces greatly elongated rectangular crystals of the salts.For this purpose, crystalline glucose is used in exactly the same manneras tri-ox'ymethylene or catechol, .25 gram thereof being a desirablequantity for additional to 460 c. c. of 98% sulphuric acid and 10 c. c.of concentrated nitric acid, the mixture being used in the sulphonationof 110 grams of resorcine.

The use of phenol in place of any of the addition agents above-mentionedlikewise produces a characteristic crystal, differing from that producedby any of the other addition agents. These crystals are substantiallyrectangular in cross section and extremely long. A desirable quantity is1 gram of crystalline phenol with 10 c. c. of concentrated nitric acidin 460 c. c. of 98% sulphuric acid, the mixture sulphonating 110 gramsof resorcine. I

The use of aluminum in the same mannerproduces crystals which are verynearly cubical and exceptionally clean. 1 gram of powder of aluminum and10 c. c. of concentrated nitric acid are added to 460 c. c. of 98%sulphuric acid, which is then used for the sulphonation of 110 grams ofresorcine. p

The use of glacial acetic acid as an addition agent produces a strikingeffect in that the salt crystals are. short, rectangular prisms withrounded corners, somewhat resembling the crystals of normal leadstyphnate. Such crystals are produced from styphnic acid, inthepreparation of which about 5c. 0. of glacial acetic acid and c. c. ofconcentrated nitric acid have been added to 460 c. c. of 98% sulphuricacid, which The use of water as an addition agent produces a salt incrystals which are nearly cubical and exceptionally firm and dense. Suchcrystals are produced from styphnic acid in the preparation of whichabout c. c. of water and 10 c. c. of concentrated nitric acid are addedto 460 c. c. of 98% sulphuric acid, which is then used for thesulphonation of grams of resorcine.

It should be remembered that the foreign substance is introduced in thesulphonation operation in the preparation of styphnic acid, and

that the described crystal shapes are those of the salts, particularlythe basic lead salt, of the acid produced by the nitration of resorcinedi sulphonic acid made in the presence of the foreign substance.

No satisfactory theoretical explanation of these effects can be oifered.The foreign substances which cause them do not fall within anyrecognized class, or appear to have any property in common other thantheir ability to change the crystal shape of basic lead styphnate fromhexagonal to generally rectangular. Limited oxidation of the resorcineor the resorcine-di-sulphonic acid may be a factor, but oxidation alonecannot account for effects which are individual to the differentaddition agents.

What is claimed is:

1. In the manufacture of a lead salt of styphnic acid by thesulphonation and nitration of resorcine to styphnic acid and thesubsequent formation of a crystalline salt therefrom, the step whichcomprises the addition of glucose to the sulphonating acid, whereby in asubsequent step said lead salt-is formed in crystals of a configurationcharacteristic to said addition.

2. In the manufacture of basic lead styphnate by a process including thesulphonation and nitration of resorcine to styphnic acid and thesubsequent formation of a crystalline salt therefrom, the step whichcomprises the addition of glucose to the sulphonating acid, whereby in asubsequent step said basic lead styphnate is formed in crystals of aconfiguration characteristic to said addition.

WILLI BRiiN.

